1. Field of the Invention
The invention relates to orthopaedic surgery. More particularly, the invention relates to tools used to prepare bones for orthopaedic implants.
2. Brief Description Of The Prior Art
Orthopaedic implant surgery typically involves the preparation of one or more bones to receive an implant stem or rod. For example, the installation of prosthetic hips and knees requires that the intramedullary (IM) canal of the femur be hollowed in order to accept the stem of a prosthetic implant. In general, the preparation of the IM canal involves the displacement of cancellous bone in order to create a cavity which will receive the stem of the implant. These cavities are usually created by one of two methods: broaching or reaming.
Broaching and reaming are quite different procedures, each having its own advantages and disadvantages. Prior art FIGS. 1 and 2 show a typical broaching tool and prior art FIGS. 3-5 show a typical reaming tool.
The broacher 10 shown in FIGS. 1 and 2 generally includes a plurality of parallel teeth 12, each having a sharp distal cutting edge 14 which is formed by distal flaring. The teeth 12 are spaced along an axis 16 of the broacher and the broacher is typically asymmetrical about the axis 16 as shown by comparing FIGS. 1 and 2. As such, the broacher 12 is well suited for creating an asymmetrical canal.
The broacher 10 is generally introduced into a pre-drilled bone canal with the aid of an impactor tool such as a hammer (not shown). The sharp edges 14 of the teeth 12 engage cancellous bone axially and displace the soft bone material within the canal. The broaching procedure may displace cancellous bone material within the bone in order to create a cavity for receipt of the stem of an implant.
Those skilled in the art will appreciate that the asymmetrical geometry of the broacher 10 may be considered either an advantage or a disadvantage depending on the surgical situation. In addition, it will be understood that the displacement of cancellous bone without removing it may also be considered an advantage or a disadvantage depending on the particular surgical situation. If the bone is structurally weak, it may be desirable to avoid removing any of the cancellous bone material. If the bone is not weak and the cancellous bone material is diseased, it may be more desirable to remove the cancellous bone material.
The reamer 20 shown in FIGS. 3-5 is generally symmetrical about its longitudinal axis 22 and is provided with at least one substantially longitudinal flute 24 defining a sharp cutting edge 26 which extends generally longitudinally along substantially the entire cutting portion of the tool. The reamer 20 has a shaft 28 which allows it to be rotated about its longitudinal axis 22 with the aid of a handle or a motor (not shown).
Those skilled in the art will know that the reamer may be provided with plural flutes and the flutes may be helically arranged. Moreover, each flute may define either one or two cutting edges. If the flutes each define only one cutting edge, the reamer will cut bone only when rotated in one (clockwise or counter-clockwise) direction. If the flutes each define two cutting edges, the reamer will cut bone when rotated in either (clockwise or counter-clockwise) direction. The cutting edges in the reamer engage the cancellous bone radially and usually displace the cut bone axially to the proximal end of the tool such that the bone is removed from the reamed canal.
It will be appreciated that the symmetrical geometry of the reamer 20 may be considered either an advantage or a disadvantage depending on the surgical situation. In addition, it will be understood that the removal of cancellous when creating a cavity for the stem of an implant may also be considered an advantage or a disadvantage depending on the particular surgical situation.
From the foregoing, it will be understood that many of the features of broachers and reamers are mutually exclusive. For example, if it is desirable to create a symmetrical cavity without removing cancellous bone material, neither the broacher nor the reamer may accomplish that result. Moreover, if it is desirable to remove some, but not all, cancellous bone material, a surgeon may need to use both a broacher and a reamer in the same bone canal.